1. Field of the Invention
The present invention relates to an image-taking lens unit and more specifically to an image-taking apparatus, such as a slim, high-variable-magnification digital camera, digital appliance with image input capability, or the like, and to an image-taking lens unit suitable therefor.
2. Description of Related Arts
Following the trend toward downsizing of digital cameras and video cameras in recent years, there have been needs for downsizing and slimming-down of image-taking lens units for use in these appliances. In addition, there have been increasing needs for slimmed-down of image-taking lens units that can be mounted in mobile phones, personal digital assistants, and the like. In response to these needs, patent publication 1 to 8 propose image-taking lens units slimmed-down by arranging a prism or a mirror in an image-taking lens system to bend an optical axis and providing the image-taking lens system as a bending optical system.    [Patent publication 1] Japanese Patent Application Laid-open No. H7-333505    [Patent publication 2] Japanese Patent Application Laid-open No. H8-248318    [Patent publication 3] Japanese Patent Application Laid-open No. 2003-169236    [Patent publication 4] Japanese Patent Application Laid-open No. 2000-187159    [Patent publication 5] Japanese Patent Application Laid-open No. 2000-187160    [Patent publication 6] Japanese Patent Application Laid-open No. 2004-102089    [Patent publication 7] Japanese Patent Application Laid-open No. 2003-156789    [Patent publication 8] Japanese Patent Application Laid-open No. 2003-43354
Generally speaking, using, as an image-taking lens system, a bending optical system whose optical axis is bent permits slimming-down of a camera body. However, in a case a zoom lens system is used as a bending optical system, most of the space for movable groups to move is provided inside the camera, which makes it difficult to reduce the volume of an image-taking lens unit in a non-photographing state even when a collapsible type is adopted (see patent publications 1 and 2, for example).
The bending optical systems disclosed in patent publications 3 and 7 each have on the most object side thereof a fixed group including a prism, and are constructed such that the prism moves in the non-photographing state and then lens elements located closer to the object side than the prism are stored into the emptied space. This construction permits some degree of slimming-down in a non-photographing state. However, in many cases, when the fixed group is arranged on the most object side, only one or so component is located closer to the object side than prism (for example, see patent publication 2). Thus, storing this lens element in the space after the movement of the prism can provide only small slimming-down and downsizing effect. Moreover, when a fixed group including a reflective surface is arranged on the most object side, in the event of an increase in the magnification variation ratio of the zoom lens system, the camera becomes too long vertically and horizontally, thus causing a problem that the projected area as viewed from the front of the camera increases.
The zoom lens systems disclosed in patent publications 4 to 6 each compose a bending optical system by arranging a reflective surface in a second lens group or between the second and a third lens groups. This construction permits slimming-down and downsizing with a high magnification variation ratio by controlling the projected surface as viewed from the front of the camera even. However, no consideration is given in this construction to slimming-down and downsizing in a non-photographing state; therefore, this construction is insufficient in terms of downsizing of the entire camera in all the states including a photographing state and a non-photographing state. Patent publication 8 discloses a bending optical system adopting a collapsible type that is capable of collapsing in the non-photographing state by tilting a mirror that bends the optical axis. This construction permits slimming-down of the camera, but results in a large change in the angles that a reflective surface forms with respect to the lens groups located closer to the object side and the image side than the mirror, thus making it difficult to maintain favorable location accuracy of the reflective surface.